1. Field of the Invention
The invention concerns a hydraulic cylinder for operating a valve of a steam turbine or the like.
2. Description of the Related Art
Hydraulic regulating means have a long tradition in gas and steam turbine construction. Concurrently with the advance of power plant technology, more and more so-called “G&S” (gas-and-steam) plants are being built in a combination process. With the aid of the hot exhaust gas of the gas turbine via a waste heat boiler, this process generates water vapor which is resupplied to the power generation process via the downstream steam turbine. Such plants have an efficiency of up to 60%. In order to master the turbines in terms of control and safety technology, a multiplicity of regulating valves and switching valves are necessary. For actuation of these valves, hydraulic cylinders generally having the form of a servo cylinder are increasingly being used. Driving the energy cylinder is achieved via an attached control block which includes a regulating valve for driving the cylinder and a quick-action stop valve through which the pressure medium may be relieved toward the tank within a minimum time period (100–200 ms) in a pressure chamber of the cylinder acting in the opening direction, so that the valve is closed by the force of a disk spring assembly.
In solutions as known, e.g., from the information brochure RE 09900/08.97 “Alles aus einer Hand-Hydraulische Regelungssysteme an Gas-und Dampfturbinen, Mannesmann Rexroth GmbH”, the quick-action stop valve and the regulating valve are arranged in a control block installed on the cylinder. In this control block all the passages for pressure medium supply and discharge are formed, so that separate conduits need not be provided in practice.
It is a problem in the formerly employed hydraulic cylinders that under particular operating conditions, vibrations in the range of the hydraulic cylinder may occur which may have a negative effect on proper operation of the associated regulating or switching valve and thus on the operation of the turbine.